Matt Smith called David Walliams "hilarious" and found it hard to take him seriously, as when he was in his prosthetics for the part he resembled a giant mole.
David Walliams' prosthetics took two hours to apply. He felt the make-up was not limiting to his acting, finding it "quite expressive".
Eager to avoid the cliché of an eerie old Victorian hotel, Toby Whithouse drew upon dreadful family vacations of his youth and instead opted for a tacky 1980s establishment.
The pictures seen on the walls throughout the episode show various aliens The Doctor has encountered such as Silurian, a Sontaran, a Judoon and a Sister of Plenitude (cat nun).
Toby Whithouse was more pleased with "The God Complex" than School Reunion (2006) and The Vampires of Venice (2010), his previous Doctor Who scripts, as the tone was darker which he was "more comfortable" writing.